1. Field of the Invention
This invention relates in general to AC motor starting circuits and more particularly to an AC motor starting circuit employing a DC power source.
2. Background of the Invention
One of the new generation advanced passive nuclear power plants supplied by the Westinghouse Electric Company LLC, Pittsburgh, Pa., known as the AP1000 Plant, has no class 1E AC power source. The plan is to use the 125VDC power station batteries to operate safety grade valves to control various aspects of the nuclear power generation process. The intent is to use DC motors to operate valves that are either too large for solenoid pilot operators or which much have a “fail-as-is” characteristic. It is anticipated that some difficulties may be encountered in procuring and then qualifying DC motors for harsh environments as would be required for deployment within the nuclear island. Furthermore, DC motors will present maintenance difficulties to the utilities due to their brushes which require periodic inspection, cleaning and/or replacement. On the other hand, many operating plants use AC motors in similar applications.
Accordingly, it would be desirable to employ AC motors that have already been qualified for nuclear applications, operated from the nuclear station's 125 volt DC battery source.
Furthermore, it is an object of this invention to provide a solid state reversing AC motor starter with a DC power source that can meet the stringent requirements of nuclear safety systems.